The degradation of tetracycline in a photo-electro-Fenton system

• The tetracycline was completely degraded in neutral photoelectro-Fenton system.
• The prepared Fe3O4–graphite cathode showed excellent electrocatalysis characteristic in electro-Fenton system.
• UV irradiation improved degradation speed and mineralization rate of tetracycline.
• The prepared Fe3O4–graphite cathode is stable and reusable.

Tetracycline is widely used in human and animal treatment of infectious disease. Because it is biologically active, stable and non-biodegradable, release to the environment threatens aquatic life and increases the risk posed by antibiotic-resistant pathogens. Therefore, treatment of this antibiotic in waste effluents is important. The degradation of tetracycline by photo-electro-Fenton oxidation was investigated in an electrolysis cell with a fabricated Fe3O4–graphite cathode. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronocoulometry were used to characterize the composite electrode. Comparisons of tetracycline degradation by electro-Fenton, UV irradiation and photo-electro-Fenton processes were investigated. Degradation efficiency was in order: photo-electro-Fenton > electro-Fenton > UV irradiation. The effects of applied current density, pH and UV irradiation on tetracycline degradation were investigated. High performance liquid chromatography (HPLC), UV–Vis absorption spectra, Fourier transform infrared spectroscopy (FT-IR) and total organic carbon (TOC) were used to investigate the decomposition of tetracycline and results showed that complete mineralization was possible. The Fe3O4–graphite cathode was stable and could be reused without catalytic decrease, suggesting its potential application in the tetracycline wastewater treatment.